I have the 4-71 DD out of my Courier 96 and I am doing a complere overhaul. I wanted to fix some messy oil leaks and pulled it out, so now it is sitting in my shop nice and handy, so I might as well have some fun with it. The head is going to a rebuilder for a reconditioning. I am installing cross head pistons with new rods and replacing the crank bearings and chequing everyting.

I've had a turbo on it for a couple of years now. It puts out about 12 psi of boost max.

The blower was rebuilt at that time with the better, harder oil seals.

I am going to change the timing from advanced to standard.

It is with a 5 speed manual Spicer and is driven "on the governor" all the time. (2500 rpm no load). (60 mph).

The rad is being recorred with dimpled tubes and serpentine fins.

I am appealing to the mechanics on the board for advise on a few things:

It has had N65 injectors so far. Should I stay with them or would you go bigger: 70, 80?

What would be a good setting for injector timing, valve clearances, Jakes?

How about a turbo boost bypass to the air box, so as to not "overload" the blower. It was discussed not too long ago on this board.

I have the DD service manual, but this won't be "stock" anymore.

I know some of you guys have experience and a lot more expertise than me on the subject, so tell me what you would do.

As you know I had this done. If you don't add an aftercooler, then the max I'd suggest is 75 injectors for 174hp and about 500lb/ft torque (1/2 of the 8V-71T). If you air to air intercool it, install the bypass blower valve (not quite sure if it was made for the 4-71 blower), and use 90 injectors, you could go as high as 225hp @ 2100rpm (more like 265hp @ 2400rpm) and 675lb/ft torque. Also, maybe install Jake brakes? Any further questions, I'd call Don Fairchild @ 661-391-4520. Good luck, TomC

Thanks TomC, I don't think I want to go with an aftercooler or intercooler. I read somewhere it would rob more power than it would make for a small engine like mine. The shop I'm getting the overhaul kit from, is also sugesting 70 or 75 injectors. My new and improved rad should be able to handle the heat from them I think. I have Jakes that I'll re-install in the head. I'll call Don F. and he'll have sugestions.

JC, I really don't understand your comment on the charge air cooler. There is nothing in the system that takes any mechanical energy other than the fan (if you have to have an auxiliary unit). If you can find a way to put it in front of the radiator, then there would be no mechanical losses to "rob" the power. Even an auxiliary fan would not have a huge power demand.

It just makes good sense to cool the air going into an engine as much as possible. It increases power and keeps the operating temperature of the combustion chamber parts (pistons, valves, etc) cooler, so that they last longer.

JC- virtually every on road Diesel, from small cars to big rigs, have air to air intercooling and turbocharging. The air to air intercooler will not take extra power (don't quite frankly know where you got that idea), it will only increase the power since it is cooling the heated turbocharged air and making it more dense-hence more air in the combustion chamber. If you have at least 4" in front of your radiator, you can just install it there. That's what I did since my bus was made with the same power train for both the 96" and 102" wide-and since my is a 102" wide, had an extra 6" in front of the radiator to play with. Even installing it on the right side with an electric fan will increase efficiency. Good Luck, TomC

Jim and Tom, I had heard I don't remember where, that the net gain between pushing the air through the plumbing to the intercooler and back vs the advantage of the cooler, more dense air would be marginal. It sounds like you are right and it would be worth doing. My rad is above the engine. The air comes from the roof and down. The fan draws the air through it, then out the bottom of the engine compartment. Upstream of the rad and right against it are shutters. Lots of space in front of the shutters. Would I remove the shutters, or keep them and mount the intercooler in front of them? When the shutters are closed, I wouln't get any air circulating through the intercooler either. Maybe I should ditch the shutters?

Unless you are in sub freezing weather, I would ditch the shutters. That small 4-71 is working hard most of the time, so cooling will be more of an issue. Also, if you get rid of the shutters, you probably will have room for the air to air intercooler. I would make sure you have the largest radiator core possible, and replace the thermostats in the engine with new 180 degree. Even back in 1980 when I bought my first truck with the 8V-92TA, it was considered to be shutterless cooling, because of better thermostats. Good Luck, TomC

Bigger the better. Positive reinforcement. More boost, cooler air, more power, more boost, cooler air, blah, blah, blah. Will work better in winter than summer, but you will need it more in hot weather. Go for it. You can make a 6 out of your 4. HB of CJ

Hey JC, i think that a year or two ago i saw a clip on a company that rebuilds steering wheels for old cars. I think it might have been on an episode of My Classic Car on the Speed channel. Might be an option for you.

Long ago in galax...... I was reading about turbos and intercoolers. The gist of this was that the intercooler "will not" boost your max HP. That number is the same for both configurations. Here is the rub: you floor it and the temp in the intake is cool. But, uit starts rising cause you are compressing air. It continues to rise to a high temp. Hot air at the intake robs your engine of power. What the intercooler does is "keep the temp down" close to the point where you first floored it. The on intercooled engine will loose power on a hill and you may need to down shift even though the fade is constant. Intercooled you can carry the hill in whatever grear will pull the hill at the bottom as the power remains constant. Maybe someone can correct me but I read where a turbo diesel makes more power AND gets better MPG than an N....or could. Seems the use of the thermal energy in the ex translates to efficiency and that means MPG. Strange world! Work real hard to get an intercooler in your design.

I think I would go with a six. People keep saying that the L10 will slip right into a DD inline six slot. I would guess that your engine compartment would accommodate a DD inline six.

I think what you have is a smoke turbo. I am easily wrong on that though. Can you go to a full turbo boost and have the engine tolerate full throttle for extended periods? Is there a four valve head available?

Good luck with this,

John

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John and everybody, I am convinced now and I am looking into installing an intercooler. I have seen them at truck wrecking yards. There is room in front of the rad. The tricky part is the plumbing. I will piece it together out of used parts and silicone connectors.

I don't want to swap my engine: I am overhauling the 4-71 that is in the bus and making the most power out of it. (Within reason). I used to drive this bus in revenue service for Brewster's in Banff, Lake Louise, Jasper, Calgary in the early 70's, and the 4-71 in it, is a big part of the nostalgic factor for me and I am not changing it. I have modern 4 stroke engines in my other bus, ( S60) and other vehicles that I enjoy for what they are. The Courier 96 is staying as stock as possible and practicle.

I remember one summer as a rookie being in Calgary in July doing 2 city tours a day in the heat of the city, ( manual steering, sky view windows, all the side windows open, taking a shower at lunch break and another one at supper time it was so hot, then doing Stampede transfers in the evening in the relative cool of the night. We also drove them up and down the Sunshine Village ski hill road before they built the gondola in '78. Lots of memories... Later with more seniority, I drove MC 5s, 7s, 8s, 9s, but none had the character of the Courier 96s. Brewster's sold them in '77 and I knew then they would make a nice motorhome. 30 years later...